Power control system for LCD monitor

ABSTRACT

A power control system for an LCD monitor having an LCD panel includes a light source unit providing light to the LCD panel, a power supply unit generating a standard low DC current, and a high-voltage generator for converting the lower DC voltage to a relatively high voltage and supplying the high voltage to the light source. The power control system further includes a feedback control unit coupled to the power supply unit for interrupting the operation of the power supply unit when the converted high voltage is determined to be abnormal. The feedback control unit includes a cable, through which a voltage can be induced due to high voltage generated by the high-voltage generator, and a power supply control circuit capable of interrupting the operation of the power supply unit when the converted high voltage is determined to be abnormal by analyzing the induced current.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Korean Application No.P2003-11049, filed on Feb. 21, 2003, which is hereby incorporated byreference as if fully set forth herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an LCD monitor, and moreparticularly, to a power control system for an LCD monitor.

[0004] 2. Discussion of the Related Art

[0005] In general, a liquid crystal display (LCD) panel included in anLCD monitor displays an image by injecting a liquid crystal into a spacebetween two thin glass plates and varying the voltage of electrodes ofthe glass plates. The LCD panel does not generate any light by itself.Therefore, it requires a light source in order to enable a user to viewan image being displayed on the LCD panel. For the reason set above, atypical LCD monitor includes an LCD panel, a lamp unit providing lightto the LCD panel, an LCD inverter and power supply (LIPS) unit supplyingthe required power to the lamp unit, and a controller controlling theLIPS system. The LIPS unit often employs a control circuit forprotecting the lamp unit from being damaged due to a power surge(voltage or current) within the lamp unit.

[0006] The control circuit directly senses the voltage (usually higherthan 600V) and current being supplied to the lamp unit. When the controlcircuit detects a voltage surge (or current surge) within the lamp unit,it reduces or cuts off the electric power being supplied to the lampunit for protecting the lamp unit by sending corresponding controlsignals. However, the control circuit described above has severalproblems. First, the control circuit is designed to protect the lampunit, but not the LIPS system. A voltage surge may occur within the LIPSsystem that still supplies a normal voltage to the lamp unit. In thiscase, the control circuit will not be able to detect such voltage surgewithin the LIPS system. In other words, the control circuit is incapableof preventing the LIPS system from being damaged when any one of thecomponents of the LIPS system does not operate properly. Themalfunctioning components and any other unit coupled to such componentswill be greatly damaged.

[0007] Next, if one or more components of the LIPS system do notoperate, they may not be properly controlled by the control circuit.Therefore, even when the control circuit detects a power surge of thelamp unit, the LIPS system may not properly reduce or cut off the powerto protect the lamp unit as indicated in the control signals, causingthe lamp unit to be even more damaged. In addition, the above controlcircuit directly senses the voltage being supplied to the lamp unit.When an abnormally high voltage (voltage surge) is feedback to thecontrol circuit, the circuit may be damaged. Therefore, a power supplycontrol system that is able to protect the lamp unit as well as a powersupply is desired.

SUMMARY OF THE INVENTION

[0008] Accordingly, the present invention is directed to a power controlsystem for an LCD monitor that substantially obviates one or moreproblems due to limitations and disadvantages of the related art.

[0009] An object of the present invention is to provide a power controlsystem for an LCD monitor, which is able to protect not only a lamp unitof the LCD monitor but also a power supply supplying power to the lampunit.

[0010] Additional advantages, objects, and features of the inventionwill be set forth in part in the description which follows and in partwill become apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

[0011] To achieve these objects and other advantages and in accordancewith the purpose of the invention, as embodied and broadly describedherein, a power control system for an LCD monitor having an LCD panelaccording to the present invention may include a light source unitproviding light to the LCD panel, a power supply unit generating astandard low DC voltage, and a high-voltage generator coupled to thepower supply unit for converting the DC voltage to a relatively highvoltage. The high voltage generator supplies the high voltage to thelight source unit. The power control system may further include afeedback control unit coupled to the power supply for interrupting theoperation of the power supply unit when the converted high voltage isdetermined to be abnormal.

[0012] The feedback control unit may include a printed circuit board(PCB) pattern, through which a voltage can be induced due to the highvoltage generated by the high-voltage generator, and a power supplycontrol circuit coupled to the PCB pattern and the power supply unit.The power supply control circuit may be integrated within the powersupply unit. The control circuit analyzes the induced voltage in orderto determine whether the converted high voltage is abnormal or not. Forexample, the high voltage may be determined to be abnormal when theinduced voltage is suddenly increased or decreased or when there is novoltage induced through the PCB pattern at all. In addition, the highvoltage may be determined to be abnormal when the induced voltage isless than a predetermined voltage level. Once the high voltage isdetermined to be abnormal, the control circuit interrupts the operationof the power supply unit, which discontinues supplying power to thehigh-high voltage generator for protection.

[0013] The power supply control circuit described above may include afirst capacitor coupled to the PCB pattern for performing AC coupling onthe induced voltage, an integration circuit coupled to the firstcapacitor for converting the AC-coupled voltage to a DC voltage byintegration, and a first diode coupled to the integration circuit andthe power supply control circuit for outputting the integrated DCvoltage to the power supply unit. The control circuit may furtherinclude a zener diode coupled to the first diode for cutting off the DCvoltage being outputted through the first diode when it is higher than abreakdown voltage of the zener diode.

[0014] It is to be understood that both the foregoing generaldescription and the following detailed description of the presentinvention are exemplary and explanatory and are intended to providefurther explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this application, illustrate embodiment(s) of theinvention and together with the description serve to explain theprinciple of the invention. In the drawings;

[0016]FIG. 1 illustrates a power control system using a feedback controlfor an LCD monitor according to the present invention; and

[0017]FIG. 2 illustrates the feedback control system 350 shown in FIG. 1in detail.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

[0019]FIG. 1 illustrates a power control system using a feedback controlfor a liquid crystal display (LCD) monitor according to the presentinvention. The power control system shown in FIG. 1 includes a coldcathode fluoresce lamp (CCFL) unit 100 providing light to an LCD panel(not illustrated) of the LCD monitor, an LCD inverter and power supply(LIPS) system 300 supplying the required electric power to the CCFL unit100, and a main controller 200. The main controller 200 generates apower control signal to the LIPS system 300 for turning the system'spower on/off, and it further generates a brightness control signal tothe LIPS system 300 for controlling the brightness of the CCFL unit 100.

[0020] The LIPS system 300 shown in FIG. 1 includes a power supply unit310 that generates a standard DC voltage upon receiving a power-onsignal from the main controller 200, a direct current to direct current(DC/DC) converter 320 that converts the standard DC voltage to apredetermined DC voltage, a high-voltage generator 330 that converts thepredetermined DC voltage to a relatively high voltage required foroperating the CCFL unit 100. The LIPS system 300 further includes abrightness controller 340 that controls the output voltage level of theDC/DC converter 320 according to a CCFL brightness control signalreceived from the main controller 200, and a feedback control unit 350that detects a power surge (abnormal voltage) of the high voltagegenerator 330 or CCFL unit 100 by analyzing a voltage induced due to thevoltage being generated by the high voltage generator 330. The controlunit 350 controls the power supply unit 310 according to the power surgedetermination.

[0021]FIG. 2 illustrates the feedback control unit 350 shown in FIG. 1in detail. According to FIG. 2, the feedback control unit 350 includes aprinted circuit board (PCB) pattern or cable provided close (notdirectly coupled) to the high voltage generator 330 or CCFL unit 100.When the high voltage generator 330 outputs a high voltage to the CCFLunit 100, a corresponding voltage is induced through the PCB pattern.Since the induced voltage is less than the high voltage, the controlcircuit may not be damaged even when the high voltage generated by thehigh-voltage generator 330 is extremely high. The feedback control unit350 further includes a first capacitor C1 which performs alternatingcurrent (AC) coupling on the induced voltage generated through the PCBpattern, and an integration circuit 351 for converting the AC-coupledvoltage to a DC voltage by integrating the AC-coupled voltage. Theintegration circuit 351 may include a resistor R1 and a second capacitorC2 as shown in FIG. 2. In addition, the feedback control unit 350 mayfurther include a diode D1 outputting the converted DC voltage, and azener diode ZD1 which cuts off the DC voltage being outputted from thediode D1 if it is higher than the breakdown voltage (or zener voltage)of the zener diode ZD1. Furthermore, the feedback control unit 350 mayinclude a power supply control circuit 352 that determines anabnormality of the voltage (e.g., voltage surge) generated by the highvoltage generator 330 by analyzing the induced DC voltage outputted fromthe diode D1. If the power supply control circuit 352 determines suchabnormality, it interrupts the operation of the power supply unit 310shown in FIG. 1 and cuts off the power being supplied to the DC/DCconverter 320. The power supply control circuit 352 may be providedexternal to the power supply unit 310 as shown in FIG. 2, oralternatively, it may be integrated within the power supply unit 310. Inthe latter case, the power supply control circuit 352 may be a switchingmode power supply (SMPS) control circuit.

[0022] Reference will now be made in detail to the operation of thepower control system shown in FIG. 1 and FIG. 2. When the power supplyunit 310 connected to an external power source (not illustrated)receives a power control signal from the main controller 200 for turningthe power on, it converts the AC input voltage (e.g., AC 100 or 220voltage) supplied by the external power source to a standard low DCvoltage necessary for operating the LCD monitor. The DC/DC converter 320coupled to the power supply unit 310 then converts the standard DCvoltage into the required half sine wave DC voltage and current. Next,the high voltage generator 330 converts the half sine wave DC voltage toa relatively high voltage (e.g., 600 V or higher) and outputs the highvoltage to the CCFL unit 100. In addition, the main controller 200outputs a brightness control signal to the brightness controller 340,which controls the output DC voltage level of the DC/DC converter 320according to the brightness control signal received.

[0023] When a voltage is induced through the PCB pattern of the feedbackcontrol unit 350 shown in FIG. 2, the induced voltage is feedback to thepower supply control circuit 352. Then the control circuit 352determines whether the voltage being generated by the high voltagegenerator 330 or being supplied to the CCFL unit 100 is abnormal (e.g.,sudden voltage drop/rise or no voltage at all) by receiving andanalyzing the induced voltage (feedback voltage). For example, the highvoltage generated by the high-voltage generator 330 may be determined tobe abnormal when the voltage induced through the PCB pattern is suddenlyincreased or decreased or when there is no voltage induced through thePCB pattern at all. Alternately, it may be determined to be abnormalwhen the induced voltage is less than a predetermined voltage levelwhich may be previously set in the power supply control circuit 352.

[0024] The abnormality of the high voltage generator 330's outputvoltage may occur when the CCFL unit 100 is in an open state or when anyone of the power supply unit 310, DC/DC converter 320, and high voltagegenerator 330 does not function properly or is damaged. When the powersupply control circuit 352 detects such abnormal voltage, it protectsthe LIPS system 300 and the CCFL unit 100 by interrupting the operationof the power supply unit 310 and cutting off the power being supplied tothe DC/DC converter 320. The power supply control circuit 352 may beprovided outside (external) the power supply unit 310 and be coupled tothe power supply unit 310 as shown in FIG. 2, or it may be providedwithin the power supply unit 310. In the latter case, the power supplycontrol circuit 352 may be a switching mode power supply (SMPS) controlcircuit of the power supply unit 310, which will determine anabnormality of the high voltage and will cut off the power beingsupplied by the power supply unit 310.

[0025] In other words, when a voltage is induced through the PCB patternshown in FIG. 2 due to the high voltage being generated by the highvoltage generator 330, then first capacitor C1 electrically connected tothe PCB pattern performs AC coupling on the induced voltage. Next, theintegration circuit (R1 and C2) converts the AC-coupled induced voltageto a DC voltage, which passes through the diode D1 and is outputted tothe power supply control circuit 352. The control circuit 352 interruptsthe operation of the power supply unit 310 if the high voltage generatedby the high voltage generator 330 is determined to be abnormal. Inaddition, the zener diode coupled to the diode D1 and the power supplyunit 310 allows the output voltage of the diode D1 to be inputted to thepower supply unit 310 if it is less than a breakdown voltage (zenervoltage). However, it cuts off the DC voltage being inputted to thepower supply unit 310 if it is higher than the breakdown voltage.

[0026] As described above in detail, the power supply control systemaccording to the present invention allows to interrupt the operation ofthe LIPS system 300 and to cut off the power being supplied by the powersupply unit 310 when the CCFL unit 100 is in an open state or when anyone of the power supply unit 310, DC/DC converter 320, and high voltagegenerator 330 does not function properly or is damaged. In this way,further damages to any other components of the LIPS system 300 can begreatly reduced.

[0027] It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A power control system for a liquid crystaldisplay (LCD) monitor having an LCD panel, the system comprising: alight source unit providing light to the LCD panel; a power supply unitgenerating a standard low direct current (DC) voltage; a high-voltagegenerator coupled to the power supply unit for converting the low DCvoltage to a relatively high voltage, the high-voltage generatorsupplying the high voltage to the light source unit; and a feedbackcontrol unit coupled to the power supply unit for interrupting theoperation of the power supply unit when the converted high voltage isdetermined to be abnormal.
 2. The power control system of claim 1,wherein the feedback control unit determines whether the converted highvoltage is abnormal or not by analyzing a voltage induced due to thehigh voltage generated by the high-voltage generator.
 3. The powercontrol system of claim 1, wherein the feedback control unit comprises acable, through which a voltage is induced due to the high voltagegenerated by the high-voltage generator.
 4. The power control system ofclaim 3, wherein the cable is a printed current board (PCB) pattern. 5.The power control system of claim 4, wherein the feedback control unitfurther comprises a power supply control circuit coupled to the PCBpattern and the power supply unit, the control circuit interrupting theoperation of the power supply unit when the converted high voltage isdetermined to be abnormal by analyzing the induced voltage.
 6. The powercontrol system of claim 5, wherein the converted high voltage isdetermined to be abnormal when the induced voltage is suddenly increasedor decreased or when there is no voltage induced through the PCB patternat all.
 7. The power control system of claim 5, wherein the convertedhigh voltage is determined to be abnormal when the induced voltage isless than a predetermined voltage level.
 8. The power control system ofclaim 5, wherein the power supply control circuit is integrated withinthe power supply unit.
 9. The power control system of claim 8, whereinthe power supply control circuit is a switching mode power supply (SMPS)control circuit.
 10. The power control system of claim 5, wherein thefeedback control unit further comprises: a first capacitor coupled tothe PCB pattern for performing alternating current (AC) coupling on theinduced voltage; an integration circuit coupled to the first capacitorfor converting the AC-coupled voltage to a DC voltage by integration;and a first diode coupled to the integration circuit and the powersupply control circuit for outputting the integrated DC voltage to thepower supply unit.
 11. The power control system of claim 10, wherein theintegration circuit comprises a resistor and a second capacitor.
 12. Thepower control system of claim 10, further comprising a zener diodecoupled to the first diode for cutting off the DC voltage beingoutputted through the first diode when it is higher than a breakdownvoltage of the zener diode.
 13. The power control system of claim 1,wherein the light source unit is a fluorescent lamp.
 14. The powercontrol system of claim 13, wherein the fluorescent lamp is a coldcathode fluorescent lamp (CCFL)
 15. A power control system for a liquidcrystal display (LCD) monitor having a LCD panel, the system comprising:a light source unit providing light to the LCD panel; a power supplyunit generating a standard low DC voltage; a direct current to directcurrent (DC/DC) converter coupled to the power supply unit forconverting the standard DC voltage to a predetermined DC voltage; ahigh-voltage generator coupled to the DC/DC converter for converting thepredetermined DC voltage to a relatively high voltage, the high-voltagegenerator supplying the high voltage to the light source unit; and afeedback control unit coupled to the power supply unit for interruptingthe operation of the power supply unit when the converted high voltageis determined to be abnormal.
 16. The power control system of claim 15,wherein the feedback control unit comprises: a printed current board(PCB) pattern, through which a voltage is induced due to the highvoltage generated by the high-voltage generator; and a power supplycontrol circuit coupled to the PCB pattern and the power supply unit,wherein the control circuit interrupts the operation of the power supplyunit when the converted high voltage is determined to be abnormal byanalyzing the induced voltage.
 17. The power control system of claim 16,wherein the power supply control circuit is integrated within the powersupply unit.
 18. The power control system of claim 17, wherein the powersupply control circuit is a switching mode power supply (SMPS) controlcircuit.
 19. The power control system of claim 16, wherein the feedbackcontrol unit further comprises: a first capacitor coupled to the PCPpattern for performing alternating current (AC) coupling on the inducedvoltage; an integration circuit coupled to the first capacitor forconverting the AC-coupled voltage to a DC voltage by integration; and afirst diode coupled to the integration circuit and the power supplycontrol circuit for outputting the integrated DC voltage to the powersupply unit.
 20. The power control system of claim 19, wherein theintegration circuit comprises a resistor and a second capacitor.
 21. Thepower control system of claim 19, further comprising a zener diodecoupled to the first diode for cutting off the DC voltage beingoutputted through the first diode when it is higher than a breakdownvoltage of the zener diode.